Control system



W. N. GITTINGS A ril 1, 1930.

CONTROL SYSTEM Filed Feb. {1, 1929 Inventor: Willium N.Gitti"ngs,

by HLS Attorney. 7

Patented Apr. 1, 1939 UNETE STATES PATENT OFFICE WILLIAM N. G-IT'IINGS, OIE UPPER DARBY, PENNSYLVANIA, ASSIGNOR T GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK CONTROL SYSTEM Application filed February 4, 1929.

occurs under certain conditions and for efiecting the stopping of the substation and for preventing its subsequent automatic starting when said predetermined abnormal condition occurs under other conditions.

In accordance with my invention, 1 provide an improved arrangement whereby a rotary transformer is automatically disconnected from its supply circuit when a predetermined current unbalance occurs in the J1 .Ll

phases oi the supply circuit after the starting operation of the transformer has been completed and then is automatically reconnected ther to when the cause of said current unalance has been removed and the phase potentials ot the supply restored to normal and whereby the rotary transformer is automatically disconnected from its supply circuit and is prevented from being reconnected thereto when the predetermined current unbalance occurs before the starting operation of the transformer has been completed.

My invention will be better understood from the following description, when taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

The accompanying drawing shows diagrammatically an automatic control arrangement, embodying my invention for eilecting the starting and stopping of a rotary transformer.

Referring to the drawing, 1 represents a rotary transformer comprising a synchronous mot r which is arranged to be connected to a polypnz e supply circuit 3 by means of asuitable circuit breaker 4 and a direct current generator 5 which is arranged to be connected to a load circuit 6 by means of a suitable circuit breaker 7. The circuit breakers 1! -l and 7 may be of any suitable type examples Serial No. 337,213.

of which are well known in the art. As shown the circuit breaker 4 is of the latched-in type and the circuit breaker 7 is of the contactor type.

In order to effect the starting of the motor generator set I provide a suitable control device 8 which when closed for a predetermined length of time effects the energization of a master relay 9. As shown in the drawing, the control device 8 is a hand switch, but it will be obvious to those skilled in the art that this may be automatically operated in any suitable manner examples of which are well known in the art.

The master relay 9 is arranged in any suitable manner examples of which are well known in the art so that whenever it is energized, it effects the starting of the motor generator set 1 and whenever it is deenergized it effects the stopping of the motor generator set 1. Since the motor generator set should be started only when it is in an operative condition and the various control devices are in the proper positions to eiiect their operation in the proper sequence, the master relay is so connected that it can be energized only when the various control devices are in predetermined positions. As shown in the drawing, I provide a single or reverse phase volt-- age relay 10 and an under-voltage relay 11 which are responsive to the voltage of the supply circuit 3 when the control device 8 is closed and which control contacts in the energizing circuit for the master relay. The undervoltage relay 11 also controls the circuit of a time relay 12 which in turn controls contacts 13 in the energizing circuit of the master relay 9. Therefore the master relay can be energized only when phase voltage of the supply circuit is correct and has remained above a predetermined value for a predetermined length of time. I also provide contacts 14, in the energizing circuit of the master relay 9, which are controlled by the circuit breaker 4 so that the master relay can be energized only when the synchronous motor 2 is disconnected from the supply circuit 3. The energizing circuit of the master relay 9 also includes contacts 15 of a relay 16, which is responsive to the excitation supplied to the synchronous motor, and contacts 17 of a relay '18 which is responsive to the voltage of the generator so that the master relay can be energized only when the motor field excitation is below a predetermined value and the generator voltage is below a predetermined value. The energizing circuit of the master relay may also include other contacts 19 and 20 controlled by suitable protective devices not shown, which respond to predetermined abnormal conditions of the motor generator set or the control apparatus therefor. Examples of such protective devices are well known in the art. After the energizing circuit of the master relay has been completed it is arranged to complete a holding circuit for its winding which is independent of a number of said contacts so that the device controlling said contacts can operate to efiect various switching operations during the starting operation of the set without effecting the deenergization of the master relay.

The master relay 9 when energized is arranged to effect the energization of a control relay 21 which in turn controls the circuit of the closing coil 22 of the circuit breaker l so as to connect the synchronous motor 2 di rectly to the supply circuit 3. I

As shown in the drawing, the field winding of the motor 2 is connected directly across the armature of the generator 5. In order, however, to prevent the motor field winding from being excited with direct current until after the speed of the motor generator set has reached substantially synchronous speed a relatively high resistance 24. is connected in series with the shunt field winding 25 of the generator 5 during t is starting operation of the set. When the motor reaches substantially synchronous speed the resistor 24 is short circuited so that suilicient current can flow through the shunt field winding 25 to build the generator voltage up to its normal value. As shown in the drawing, the synchronous-speed responsive device is relay 26 which is connected in series relation with the motor field winding by news of a current transformer 2 During the star ing operation sufficient alternating current flows through the relay 25 to maintain its contacts 28 open. When, however, the motor reaches synchronous speed, the relay closes its contacts 28 and short-circuits the resistor 24. This particular arrangement for controlling the excitation of the motor during the starting operation is disclose: and claimed in the copending application Serial No. 212,952 filed August 15, 1927by Eugene L. Hough and assigned to the assignee of this application.

A ter the generator voltage has increased to a sufficient value to cause the motor field current relay 16 to close its contacts and the voltage relay 18 to close its contacts 48,

and the polarity of the generator is correct in response to the energization of the master relay 9 and to be deenergized in any suitable manner after the start-ing operation of the transformer has been completed. As shown in the drawing, the deenergization of the time relay 31 is effected by means of a current directional relay 32 which is responsive to the direction of current flow between the generator 5 and the load circuit 6. When current flows from the generator 5 to the load circuit the directional relay 32 opens the energizing circuit of the time relay 31. In case the directional relay 32 fails to open its contacts forany reason, within a predetermined time after tne master relay 9 is energized, the time relay 31 effects the energization of a suitable lockout relay 33 which controls contacts 40 in the circuit of the master relay 9 so as to effect the deenergization of the master relay. The lockout relay 33 is designed iii-any suitable manner so'that its contacts are not automatical y reset when the relay is deenergized.

In accordance with the preferred embodiment of my invention shown in the drawing, I provide an improved arrangement for con trolling the stopping and starting of the rotary transformer 1 in response to a predetermined unbalance current condition in the supply circuit 3. In case a fault such as a short-circuit or an open-circuit occurs on the supply circuit 3, while the transformer is in operation, it is desirable to shut the transformer down until the fault has been removed. As soon as the fault on the supply circuit has been removed it is then desirable to restart the transformer and reconnect it to the load circuit. In case, however, a fault occurs in the motor 2 of the transformer which causes a similar current unbalance, it is desirable to shut down the transformer and keep it shut down until after it has been inspected by an operator. In accordance with my invention, I accomplish these results by providing a suitable phase balance current relay 35 which is connected and arranged in any suitable manner examples of which are well known in the art so that it closes its contacts 36 whenever a predetermined unbalance occurs between the currents in any two phases of the supply circuit 3. The contacts 36 of the current relay 35 are so connected with contacts of the voltage relay 18 that: if the contacts 36 are closed when the V voltage of the generator is above a predetermined value, the deenergization of the master relay 9 is effected to shut down the rotary transformer 1. is soon as the proper voltage conditions are subsequently restored on the supply circuit 3, the master relay 9 is again reenergized to effect the automatic restarting of the rotary transformer. If the contacts 36 of the relay 35 are closed however when the voltage of the generator is below a predetermined value, a circuit for the lookout relay 33 is completed to effect the deenergization of the master relay 9 and the shutting down of the rotary transformer 1. Since however, the contacts of the lookout relay 33 remain open after the relay is deenergized, the subsequent restoration of normal voltage conditions on the supply circuit 3 does not effect the automatic restarting of the rotary transformer 1.

The operation of the arrangement shown in the drawing is as follows:

In order to start the rotary transformer 1 the control switch 8 is closed, thereby connecting the reverse phase voltage relay 10 and the undervoltage relay 11 across the supply circuit 3. If the proper voltage conditions exist on the supply circuit 3 these voltage relays close their respective contacts. The undervoltage relay 11 by closing its contacts 38, completes an energizing circuitfor the time relay 12. After a predetermined time, the time relay 12 closes its contacts 13 and completes an energizing circuit for the master relay 9. This energizing circuit of the master relay 9 also includes contacts 39 of the reverse phase voltage relay 10, auxiliary contacts 14 on the circuit breaker 4, contacts 15 of the motor field relay 16, contacts 17 of the generator voltage relay 18, protective contacts 19 and 20, contacts 40 of the lockout relay a3 and contacts 38 of the undervoltrelay 11. The master relay 9 by closing its contacts 41 completes a locking circuit for itself which is independent of the contacts 13, 39, 14. 15 and 17 so that the subsequent opening of these contacts during the starting 0 aeration of the rotary transformer does not effectthe deenergization of the master relay. The master relay 9 by closing its contacts 42 completes through auxiliary contacts 43 on the circuit breaker 4 an energizing circuit for the hesit-ating control relay 21. The control relay 21 when energized completes through its contacts as and the contacts 42 of the master relay 9 an energizing circuit for the closing coil 22 of the circuit breaker 4. The circuit breaker 4, when closed, connects the armature winding of the motor 2 directly across the supply circuit 3 so that the motor starts as an induction motor and accelerates to substantially synchronous speed.

"Jv hile the motor 2 is ooerating below synchronous speed during the starting thereof an alternating current voltage is induced in its field circuit which causes sufficient current to .fiow through the current relay 26 to maintain the contacts of this relay open. Therefore, until the motor reaches substantially synchronous speed, the resistor 24 con nected in series with theshunt field winding 25 of the generator 5 so that the generator voltage does not build up. Vvhen, however, the motor reaches substantially synchronous speed, the induced current through the winding 26 decreases to such a low value that the contacts 28 are closed and together with the contacts 15 of the master relay 9, complete a short-circuit around the resistor 24:.

lVhen the resistor 24 is short-circuited the generator voltage starts to build up and direct current begins to flow through the motor field winding. When the direct current through the motor field winding reaches a predetermined value, the relay 16, which is designed in any suitable manner so that it does not respond to alternating current induced in the motor field circuit during the starting operation, opens its contacts 15 and closes its contacts e6. The closing of the contacts 46 completes an energizing circuit for the closing coil 30 of the circuit breaker when the voltage of the generator has a predetermined polarity so that the contacts l? of the polarity relay 29 are closed and is above a predetermined value so that the con tacts 48 of the generator voltage relay 18 are closed. This energizing circuit of the closing coil 30 is completed across the terminals of the generator 5 and also includes the contacts 49 of the master relay 9.

As soon as the circuit breaker 7 closes and current flows from the generator 5 to the load circuit 6 the current directional relay opens its contacts 50 in the energizing circuit of the time relay 31, which was completed through contacts 51 of the master relay 9 when it was energized. The rely therefore, prevents the time relay 31 from clof its contacts 52 and thereby effecting the gization of the lookout relay 33, if the starting operation is completed within a pre letermined time after the master relay 9 is ener gized. If, for any reason, the relay 32 main tains its contacts 50 closed for a predetermined time while the master relay 9 is energized the time relay 31 closes its contacts 52 and completes through contacts of the master relay an energizing circuit for the lockout relay 33. Thus relay 33 by opening its contacts 10 in the holding circuit of the master relay 9 effects the shutting down of the transformer, and prevents the restarting thereof until the contacts =10 have been reset.

hen the voltage relay 18 01 crates in response to a voltage above a predetermined value, its contacts 53 complete a circuit around the contacts 28 of the relay 26 so that any inductive disturbance in the motor field circuit after the starting operation has been completed, cannot open the short circuit around the resistor 24 in the shunt field circuit of the generator.

If a fault, which produces a predetermined unbalance between the currents in an two phases of the supply circuit 8, occurs while the transformer 1 is inoperation, the current balance relay 35 closes its contacts 36 and completes, through contacts 54 of the generator voltage relay 18, a short-circuit around the coil of the under-voltage relay 11 so that this relay opens its contacts 38 in the holding circuit of the master relay 9. In order to limit the current through the contacts 36 and 53, a resistor 55 is connected in series therewith. lvhen the master relay 9 is deenergized its contacts 56 connect the direct current trip coil 57 of the circuit breaker e across the terminals of the generator 5 and its contacts 58 connect the alternating current trip coil 59 and the auxiliary contacts 60 on the circuit breaker 4 across a suitable source of alternating current which in the arrangement shown in the drawing is one phase of the supply circuit 3. The two trip coils 57 and 59 are provided so that in case phase which supplies current to' the alternating current trip coil is the phase on which the fault exists the circuit breaker 4: is tripped by the voltage available across the generator 5.

After the master relay 9 has been deenergized it cannot be reenergized to effect the restarting of the transformer 1 until the speed of the transformer has decreased below a value sufficient to cause the relays 16 and 18 to close their respective contacts 15 and 1?. Also the master relay 9 cannot be reenergized until the voltage conditions on the supply circuit 3 have been restored to normal so that the contacts 39 of the reverse phase voltage relay 10 and the contacts 38 of the undervoltage relay 11 are closed.

If the fault which caused the transformer to be disconnected from the supply and load circuits occurred on the supply circuit the restarting of the transformer cannot be effected until the fault has been removed since the reverse phase voltage relay will not close its contacts 39 until all of the pha e voltages are substantially normal and have the proper phase rotation. As soon as the voltage conditions of the supply circuit are restored to normal and the relays 16 and 18 have been restored to their deenergized positions the above traced energizing circuit for the master relay 9 is completed and the rotary transformer is automatically started and connect ed to the load circuit 6 in the manner above described. 7.

If the fault occurs in the motor 2, the voltages of the supply circuit 3 are restored to normal as soon as the circuit breaker 4 is opened to disconnectthe motor from the sup ply circuit 3. Therefore, as soon as the speed of the transformer has decreased to a sumcient value to cause the relays 16 and 18 to move to their deenergized positions, the master relay 9 is again energized and the circuit breaker i is reclosed to reconnect the motor to'the supply circuit. If the fault still exists in the motor, when the circuit breaker at is reclosed the phase balance current relay 35 again closes its contacts 36 and immediately completes an energizing circuit for the lockout relay 33 through the contacts 61 of the generator voltage relay 18 which is now in its deenergized position and the contacts 51 of the master relay 9. The lockout relay 33 by opening its contacts 40 effects the permanent deenergization of the master relay 9 so that the master relay cannot be again energized to effect the restarting of the transformer 1 until the contacts of the lookout relay have been reset by hand.

Therefore it will be observed that whenever the current balance relay contacts 36 are closed when the voltage relay 18 is in its energized position, the motor generator is shut down and is automaticall Y restarted when conditions are restored to normal and wherever the contacts 86 are closed when the voltage relay 18 is in its deenergized position, the motor generator is shut down and prevented from being automatically restarted when the abnormal conditions have been restored to normal.

While I have, in accordance with the patent statutes, shown and described my invention as applied to a particular system and as embodying various devices diagrammatically indicated, changes and modifications willbe obvious to those skilled in the art and 1, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit andscope of my invention.

l/Vhat I claim as new and desire to secure by Letters Patent of the United States, is:

1. In combination, a polyphase supply circuit, a rotary transformer, a control device, means normally arranged to efiect the connection of said transformer to said circuit in response to a predetermined condition of said control device, means responsive to a predetermined relation between the currents in different phases ofsaid circuit, means responsive to a predetermined electrical condition of said transformer, and means controlled directly by said current responsive means and said transformer electrical condition responsive means for effecting the disconnection of said transformer from said circuit and the subsequent reconnection thereto whenever a predetermined current condition occurs in said circuit when said transformer electric condition responsive means is in a predetermined position and for effecting the disconnection of said transformer from said circuit and for rendering said connection means non-responsive to said control device whenever said predetermined current condition occurs when said transformer electrical condition responsive means is in another positicn.

2. In combination, a polyphase supply circuit, a rotary transformer, and automatic switching means for controlling the connection between said circuit and rotary transformer including a control device, means normally arranged to effect the connection of said transformer to said circuit in response to a predetermined operation of said control device, means responsive to a predetermined relation between the currents in different phases of said supply circuit, means responsive to the voltage of said transformer, and means controlled directly by said current responsive means and said voltage responsive means for efiect-ing the disconnection of said transformer from said circuit and the subsequent automatic connection thereto whenever a predetermined current condition occurs while said voltage relay is in a predetermined position and for effecting the disconnection of said transformer from said circuit and rendering said connecting means inoperative to effect the subsequent connection of said transformer to said circuit whenever said predetermined current condition occurs while said voltage relay is in another position.

3. In combination, a polyphase supply circuit, a motor generator set, a control device, means normally arranged to effect the connection of the motor of said set to said circuit in response to a predetermined condition of said control device, means responsive to a predetermined relation between the currents in different phases of said circuit, a relay responsive to the voltage of the generator of said set and means controlled by said current responsive means and said relay for effecting the disconnection of the motor from said circuit and the subsequent connection thereto to said circuit whenever predetermined current conditions occur while said relay is energized more than a predetermined value and for eflecting the disconnection of said motor from said circuit and for rendering said connecting means unresponsive to said control means whenever said predetermined current conditions occur While said relay is energized less than said predetermined value.

4. In combination, a polyphase supply circuit, a motor generator set, a control device, means normally arranged to effect the connection of the motor of said set to said circuit in response to predetermined condition of said control device, a phase balance current relay connected to said circuit, a relay responsive to the voltage of the generator of said set, and means controlled by said relays for effecting the disconnection of said motor from said circuit and the subsequent reconnect thereof to said circuit whenever a predetermined current unbalance occurs while the generator voltage is above a predetermined value and for effecting the disconnection of said motor from said circuit and for preventing the automatic reconnection thereof to said circuit whenever said predetermined current unbalance occurs when the generator voltage is below a predetermined value.

5. In combination, a polyphase supply circuit, a motor generator set, means including a master relay for effecting the connection of the motor of said set to said circuit when said relay is energized and the disconnection of said motor from said circuitwhen said relay is deenergized, a circuit for said master relay, a plurality of normally closed contacts in said relay circuit, a phase balance current relay connected to said supply circuit, a relay responsive to the voltage of said generator, and means controlled by said current and voltage relays for effecting the temporary opening of certain of said normally closed contacts whenever a predetermined current unbalance occurs when the generator voltage is above a predetermined value and for effecting the permanent opening of other of said normally closed contacts whenever said predetermined current unbalance occurs when the generator voltage is below a prede- 

